So far, as a structure for supplying electric power to each auxiliary machine such as a power window motor or a door lock unit in a slide door, which is seen in an one-box car or some passenger cars, various measures have been adopted in order to connect each auxiliary machine to a wiring harness on the side of a vehicle body (i.e. on the side of a power source) through a door wiring harness.
For example, a conventional structure for supplying electric power is a structure, in which a signal is transmitted from the side of a vehicle body to each auxiliary machine on the side of the slide door by using electric wires that moves as the slide door is slid. However, this structure has a problem that the electric wires are bent as the slide door is repeatedly opened and closed causing the electric wires being broken. Moreover, the electric wires are seen when the slide door is opened or closed causing damage to the outside appearance.
Another conventional structure for supplying electric power is disclosed in Japanese Utility Model Laid-Open No. H4-124555. In this structure, the side of a vehicle body, which has a slide door slidable back and forth, is provided with a first power supply terminal that connects to the side of a battery, while the side of the slide door is provided with a second power supply terminal that connects to the side of a door control device, wherein the first power supply terminal is provided with a movable terminal surrounded by an insulating member, the movable terminal being separable from the first power supply terminal, wherein the movable terminal is pressed and held by an end of the second power supply terminal when the slide door is closed, thereby connecting the first and second power supply terminals.
However, the structure described above has a drawback in points that the current-carrying is performed only when the slide door is closed and that when the door is opened even a little the action of an auxiliary machine such as opening or closing of a power window is not performed, and that it is impossible to take a measure such as preventing being caught from occurring. Further, since the structure described above is a double-contacts structure, in which the first and second power supply terminals are connected to each other through the movable terminal for dust-proofing and waterproofing, therefore causing increase in contact resistance and deterioration in reliability of electric connection.
For the purpose of solving the above problem, there has been proposed an idea for employing a technique, in which the electric power and the data are transmitted in a noncontacting manner utilizing electromagnetic coupling. An example of such a technique is a noncontacting data-carrier system as disclosed in Japanese Patent Application Laid-Open No. H8-316895. In such a noncontacting communication system, mainly, a communication is performed between a base IC that carries out reading and writing of the data and a transponder IC that stores the data in advance. Since the transponder IC do not have a power source, the base IC generates a large resonance output by electromagnetic induction so that the supply of the electric power and transmitting of the data are simultaneously performed.
However, in the nonocontacting communication system described above, since the large resonance output causes a noise release to surrounding equipment, therefore it is difficult to perform the communication by electromagnetic coupling in such a manner in an area in which surrounding equipment of a motor vehicle and so on stands close to one another.
Further, in the electromagnetic induction communication, the resonance output of the receiving-side is supplied to the transmitting-side, then the output is impedance-modulated synchronously with serial data, so that a change in current on the receiving-side is outputted serially. Therefore, the action becomes passive, causing a difficulty in application to various communication modes, because important is an action of the receiving-side, the action being synchronous with an event output of the transmitting-side.
In order to attain bidirectional communication between two communication units as a noncontacting communication system, in which electromagnetic coupling appropriate for mounting on a vehicle is utilized, it can be considered that communication of only data is performed by using electromagnetic coupling, while power is separately supplied to each communication unit not by using electromagnetic coupling. In such a case, magnetic field can be reduced minimal necessary for transmitting and receiving only the data, therefore the noise can be prevented from being released to the outside, thereby attaining data communication in a noncontacting manner in a limited area.
An example of the noncontacting communication system described above has been proposed by the present applicant in Japanese Patent Application No. 2002-143384 titled as “noncontacting short-range communication device for slide door”. This communication device includes a rail provided in a vehicle body; a slide part provided in a slide door sliding being guided by the rail; a first antenna member attached to the rail in the longitudinal direction of the rail; a second antenna member provided in the slide part so as to face to the first antenna member closely; a first communication unit provided on the side of the vehicle body being connected to the first antenna member; and a second communication unit having the same constitution as that of the first communication unit, the second communication unit being provided on the side of the slide door being connected to the second antenna member, wherein the first and second communication units transmit or receive data by electromagnetic induction coupling between the first and second antenna members.
In the noncontacting short-range communication device for a slide door, required is a circuit construction that excellently performs a bidirectional data communication using electromagnetic coupling.
Further, in the bidirectional data communication using electromagnetic coupling, if a constant communication in a vehicle is taken into consideration, it is necessary to have a security function as to the communication data because of a possible malfunction due to external magnetic field. As such a security function, for example, considered is a manner, in which the same ID code is recognized between the bidirectional communication units (such as ECU of the vehicle) so that the permission of driving is given.
However, for example, when one ECU out of the pair of the ECU is damaged, since the pair of the ECU in the bidirection stores the same ID code initially set in advance, therefore it is necessary to switch the other normal ECU simultaneously, causing deterioration in maintenance and increase in the repair cost.
It is therefore an objective of the present invention to solve the above problems and to provide a noncontacting short-range communication device for a slide door, which includes a circuit construction for excellently performing the bidirectional data communication between the side of a vehicle body and the side of the slide door using electromagnetic induction coupling.
It is another objective of the present invention to provide a noncontacting short-range communication device for a slide door, which includes a circuit construction for excellently performing the bidirectional data communication between the side of a vehicle body and the side of the slide door using electromagnetic induction coupling and has an excellent maintenance and inexpensive repair cost.